Engine Throttle issues

red5.0fox · Nov 12, 2022

So I’ve been having an issue with my 1992 5.0 for a while now. I’ll go through what all is done to it first. Explorer heads/intake, CAI, 24lb injectors/maf, 70mm tb and spacer, and POSSIBLY a cam. I haven’t been in the motor but it is from a different car. The issue I’m having is that if any throttle is applied, there is no response. In fact, it almost dies. Sometimes it does. Here’s what I have done. I’ve checked fuel pressure, it checked out, also used a smoke machine to check for leaks, solved all of them except for a leak in the EGR valve. There was little to no change. I’m really lost on what could be the issue and I’d love to hear some ideas. If anyone needs more details let me know!

Potomus Pete · Nov 13, 2022

Seems like the Throttle Position Sensor to me, but hard to tell over the internet. Mine had the same syptoms as you and thats what it was. Did it run good at one time, bacause your 24lb injectors need to match your MAF of coarse.

General karthief · Nov 13, 2022

I giggle to myself (I prolly do that more that I think) when someone says "and it's got a cam" like a stock engine doesn't have one, just one of those things people say that begs for a comeback from Jeff Foxworthy.
I agree with Pete, the TPS is suspect here.
But I must ask, people also say things like 'it's got fuel pressure ' but how much, just some fuel spurting out the schrader valve don't mean anything in the real world of EFI mechanics.
Don't take offence to any of this, EFI is more technical than people think, still pretty easy but technical, where in the past we could use a match stick (do they still have those?) to get a engine running now you need to take a reading from a gauge or meter.
Also you don't say if this is a new issue or you got it not running correctly. This can be an important factor. Some just don't know how to fix these cars and will sell a problem, then you have the 'flippers' that will dump a car they either created the problem or just couldn't fix.
Ok, now that I've bored you to death with my coffee induced rant let me introduce you to the 'surging idle checklist' put together by some of the finest minds in the land of mustangs (and mine was NOT one of them), the lead taken by jrichker, still Stangnets favorite tool, read the directions, I know, we're guy's and 'we don't need no stink'n directions ', trust me, it's a tech thing.

Help me create the "Surging Idle Checklist"

Updated 26-Oct-2019 to clarify creeping idle RPM increase as the car is being driven. Many of you are familiar with the "Cranks OK, but No Start Checklist for Fuel Injected Mustangs" checklist and the No Crank Checklist. They are very effective in finding and eliminating the problems by use of...

forums.stangnet.com

It will give you the correct way to check the TPS.
But maybe you're an experienced mechanic and I just waisted my time making you roll your eyes and utter duh a couple times, ohhhky I'll just hit the 'post reply' button and fetch myself another cup of coffee.

Potomus Pete · Nov 13, 2022

This guy is eighteen. These lists that were created are a perfect way to get to really know your car. If you go step by step you will really get to know what our cars are about. You can get a permenant gauge that comes off your Schrader valve so you can see whats going on.

red5.0fox · Nov 13, 2022

General karthief said:
I giggle to myself (I prolly do that more that I think) when someone says "and it's got a cam" like a stock engine doesn't have one, just one of those things people say that begs for a comeback from Jeff Foxworthy.
I agree with Pete, the TPS is suspect here.
But I must ask, people also say things like 'it's got fuel pressure ' but how much, just some fuel spurting out the schrader valve don't mean anything in the real world of EFI mechanics.
Don't take offence to any of this, EFI is more technical than people think, still pretty easy but technical, where in the past we could use a match stick (do they still have those?) to get a engine running now you need to take a reading from a gauge or meter.
Also you don't say if this is a new issue or you got it not running correctly. This can be an important factor. Some just don't know how to fix these cars and will sell a problem, then you have the 'flippers' that will dump a car they either created the problem or just couldn't fix.
Ok, now that I've bored you to death with my coffee induced rant let me introduce you to the 'surging idle checklist' put together by some of the finest minds in the land of mustangs (and mine was NOT one of them), the lead taken by jrichker, still Stangnets favorite tool, read the directions, I know, we're guy's and 'we don't need no stink'n directions ', trust me, it's a tech thing.

Help me create the "Surging Idle Checklist"

Updated 26-Oct-2019 to clarify creeping idle RPM increase as the car is being driven. Many of you are familiar with the "Cranks OK, but No Start Checklist for Fuel Injected Mustangs" checklist and the No Crank Checklist. They are very effective in finding and eliminating the problems by use of...

forums.stangnet.com

It will give you the correct way to check the TPS.
But maybe you're an experienced mechanic and I just waisted my time making you roll your eyes and utter duh a couple times, ohhhky I'll just hit the 'post reply' button and fetch myself another cup of coffee.

I am familiar with him lol, he’s a genius. I’ve found multiple problems off his checklist in the past lol. I tested fuel pressure the way he said to do it (while also checking the regulator). I retested it again today (just to double check myself) and the test gauge was in the “late timing” area. Messed with the timing to try to get it to run better, no luck. It has been doing this hesitation for a bit now (month or 2) but it only got to the point of practically 0 drivability yesterday. And yes, I definitely can see how efi is very technical lol. I am young, I know nowhere near everything, so I’ve been reading up on some efi mustang books to try and learn some stuff. I’ll get out there and test the tps voltage today and report back.

red5.0fox · Nov 13, 2022

Potomus Pete said:
This guy is eighteen. These lists that were created are a perfect way to get to really know your car. If you go step by step you will really get to know what our cars are about. You can get a permenant gauge that comes off your Schrader valve so you can see whats going on.

I’ve been wanting to invest in some quality gauges to see what’s going on 24/7 just haven’t had the money unfortunately

red5.0fox · Nov 13, 2022

Potomus Pete said:
Seems like the Throttle Position Sensor to me, but hard to tell over the internet. Mine had the same syptoms as you and thats what it was. Did it run good at one time, bacause your 24lb injectors need to match your MAF of coarse.

Yes, it used to run pretty well. I’ve had the setup since this past summer (May/June) and had almost 0 issues. This problem has only surfaced within the past couple months. And the Maf is a BBK 24lb maf.

Potomus Pete · Nov 13, 2022

red5.0fox said:
I am familiar with him lol, he’s a genius. I’ve found multiple problems off his checklist in the past lol. I tested fuel pressure the way he said to do it (while also checking the regulator). I retested it again today (just to double check myself) and the test gauge was in the “late timing” area. Messed with the timing to try to get it to run better, no luck. It has been doing this hesitation for a bit now (month or 2) but it only got to the point of practically 0 drivability yesterday. And yes, I definitely can see how efi is very technical lol. I am young, I know nowhere near everything, so I’ve been reading up on some efi mustang books to try and learn some stuff. I’ll get out there and test the tps voltage today and report back.

Your going to get it soon.....If your able to use a multimeter test the TPS

red5.0fox · Nov 14, 2022

Alright, an update. Haven’t had the chance to get out and do any testing until earlier tonight. I went through with a base idle reset that I watched from Brew2l, did my tps (it was around .60v, bumped it up to about .98) so the tps is good. Messed with my timing using a timing light, still not 100% sure that it’s perfect, it’s pretty hard for me to make out the numbers on it so I’m really not sure where it even is, just got it to where it seemed to be running the cleanest (I’ll try and mark the correct areas and recheck it). Let it sit w/o the battery for a while, then started it up and did his little run for 2 minutes stuff. I was never actually able to rev the car (it was like 12AM here) so I’m not 100% sure if it is still messed up or works, the idle seemed alright. But While it was running with the loads on (dome light, headlights, ac, hazards, and steering wheel turned) I noticed the amp (or is it volts?) gauge was super low. Just barely above the red mark of 8. Is that normal for these cars running max loads? I do know the alternator in them sucks. I’ve also come to the conclusion the fox has some sort of AFTERMARKET cam in it (because all foxes have cams ). Makes sense since when I pulled the valve covers off this engine, it had crane roller rockers and pushrods in it. Feel like you really only do that after a cam upgrade. So maybe that’s part of what is causing my issues is I’m treating this like a car with a stock cam. Who knows. I’ll run through some of the idle checklist tomorrow and see if I can’t find any more kinks. Mean while, anyone have any other possible ideas?

General karthief · Nov 15, 2022

The alternator in these cars are adequate at best but they should charge 13 volts + a little at idle with a load (lights, ac ) as long as the idle is set (750+ rpms) right. Sounds like yours needs replacement.
EFI cars need good steady power or they get angry and act up. Good grounds are a must also.

red5.0fox · Nov 15, 2022

General karthief said:
The alternator in these cars are adequate at best but they should charge 13 volts + a little at idle with a load (lights, ac ) as long as the idle is set (750+ rpms) right. Sounds like yours needs replacement.
EFI cars need good steady power or they get angry and act up. Good grounds are a must also.

Suppose I should look into one. I actually think it’s an auto store replacement that I’ve had for a bit, but we all know how reliable those are. I’m starting to wonder if it is electrical issues. Not sure if It has anything to do with it but sometimes my ac controls work, sometimes they don’t. Weird issues for sure!

red5.0fox · Nov 15, 2022

I have been doing some other reads too and am wondering if it’s my fuel pump. It’s the stock one, hasn’t been replaced, and ofc I’m running 24lb injectors and such. Maybe it’s just failing? When the car is running the fuel pump is almost louder than the exhaust with that whine it makes. Wonder if I should invest in one of those and a fuel filter. I am very broke though and money is not coming easily so could someone point me towards a good test?

AeroCoupe · Nov 15, 2022

Stop. You need to address the charging issue. Start with taking the alternator to the parts store (hope it has a warranty) and have them load test it. If it is bad then replace and try loading it on the car again with all the accessories and see what happens. If it is good then reinstall and you need to do a voltage drop test on all the cables. Hell I would recommend it regardless of the alternators health.

Howto perform charging system voltage drop test

To anyone else reading any of my posts I usually include the line: Today's cars simply will not run right without a strong battery and charging system! Cut corners here at your own risk I'm a big believer in starting with the basics. As such I...

stangnet.com

Once you have fixed and/or verified that the charging system and cables are good that may very well fix all your issues. Remember, fuel pumps will not pump the same on 8V as they do on 14V.

red5.0fox · Nov 15, 2022

AeroCoupe said:
Stop. You need to address the charging issue. Start with taking the alternator to the parts store (hope it has a warranty) and have them load test it. If it is bad then replace and try loading it on the car again with all the accessories and see what happens. If it is good then reinstall and you need to do a voltage drop test on all the cables. Hell I would recommend it regardless of the alternators health.

Howto perform charging system voltage drop test

To anyone else reading any of my posts I usually include the line: Today's cars simply will not run right without a strong battery and charging system! Cut corners here at your own risk I'm a big believer in starting with the basics. As such I...

stangnet.com

Once you have fixed and/or verified that the charging system and cables are good that may very well fix all your issues. Remember, fuel pumps will not pump the same on 8V as they do on 14V.

Probably good to do nonetheless for sure, I’ll take it out next chance I get. When it’s idling with no loads it seems to be around the middle of the gauge, but the problem still persists, maybe that’s still to low? Come to think of it, before my problem got this bad the charging gauge used to be pretty high, between the middle and max volts displayed. So maybe it is an issue..

red5.0fox · Nov 15, 2022

Good evening fellow stang enthusiasts. Just finished changing my alternator with another one we had lying around which was deemed good by the autostore not to long ago. Unfortunately none of my issues were fixed, however I did turn everything on (minus the ac, it didn’t seem to want to blow air today) and the volt gauge didn’t change to drastically. So maybe that is fixed. To confirm, I will take the alternator I took out and get it tested tomorrow. But, I have seemingly crossed that off the list. Tomorrow I also plan to begin the surging idle checklist and check everything. The one other thing I haven’t messed with yet thag I feel could be an issue is timing. After all, I have no CEL, and bad timing doesn’t cause a cel (to my knowledge). If anyone else has any nuggets of wisdom please let me know!

red5.0fox · Nov 15, 2022

red5.0fox said:
Good evening fellow stang enthusiasts. Just finished changing my alternator with another one we had lying around which was deemed good by the autostore not to long ago. Unfortunately none of my issues were fixed, however I did turn everything on (minus the ac, it didn’t seem to want to blow air today) and the volt gauge didn’t change to drastically. So maybe that is fixed. To confirm, I will take the alternator I took out and get it tested tomorrow. But, I have seemingly crossed that off the list. Tomorrow I also plan to begin the surging idle checklist and check everything. The one other thing I haven’t messed with yet thag I feel could be an issue is timing. After all, I have no CEL, and bad timing doesn’t cause a cel (to my knowledge). If anyone else has any nuggets of wisdom please let me know!

Also if it means anything, I cleaned the battery terminals, alternator connections, and tested the battery while the car was running and it was a steady 14.6v

Mr.Blake · Nov 21, 2022

red5.0fox said:
So I’ve been having an issue with my 1992 5.0 for a while now. I’ll go through what all is done to it first. Explorer heads/intake, CAI, 24lb injectors/maf, 70mm tb and spacer, and POSSIBLY a cam. I haven’t been in the motor but it is from a different car. The issue I’m having is that if any throttle is applied, there is no response. In fact, it almost dies. Sometimes it does. Here’s what I have done. I’ve checked fuel pressure, it checked out, also used a smoke machine to check for leaks, solved all of them except for a leak in the EGR valve. There was little to no change. I’m really lost on what could be the issue and I’d love to hear some ideas. If anyone needs more details let me know!

Engine Throttle issues

red5.0fox

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Potomus Pete

I'm still waiting for the fully nude shots

General karthief

wonder how much it would cost to ship you a pair

Help me create the "Surging Idle Checklist"

Potomus Pete

I'm still waiting for the fully nude shots

red5.0fox

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Help me create the "Surging Idle Checklist"

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red5.0fox

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General karthief

wonder how much it would cost to ship you a pair

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lube between the nut and the face. I know my lubes

Howto perform charging system voltage drop test

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Howto perform charging system voltage drop test

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